Method and apparatus for video coding

ABSTRACT

An apparatus for video decoding includes processing circuitry. The processing circuitry can be configured to receive data of a current block coded with an intra block copy (IBC) mode in a bitstream. A block vector of the current block can be determined based on a history-based block vector prediction (HBVP) table that includes one or more entries each corresponding to a previously decoded block. Each entry can include a block vector of the corresponding previously decoded block and a location of the corresponding previously decoded block. The current block can be reconstructed based on the determined block vector of the current block.

INCORPORATION BY REFERENCE

This present disclosure claims the benefit of U.S. ProvisionalApplication No. 62/867,658, “History Based Block Vector Prediction forIntra Picture Block Compensation” filed on Jun. 27, 2019, which isincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GBytes of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce the aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signals is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision distribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

Motion compensation can be a lossy compression technique and can relateto techniques where a block of sample data from a previouslyreconstructed picture or part thereof (reference picture), after beingspatially shifted in a direction indicated by a motion vector (MVhenceforth), is used for the prediction of a newly reconstructed pictureor picture part. In some cases, the reference picture can be the same asthe picture currently under reconstruction. MVs can have two dimensionsX and Y, or three dimensions, the third being an indication of thereference picture in use (the latter, indirectly, can be a timedimension).

In some video compression techniques, an MV applicable to a certain areaof sample data can be predicted from other MVs, for example from thoserelated to another area of sample data spatially adjacent to the areaunder reconstruction, and preceding that MV in decoding order. Doing socan substantially reduce the amount of data required for coding the MV,thereby removing redundancy and increasing compression. MV predictioncan work effectively, for example, because when coding an input videosignal derived from a camera (known as natural video) there is astatistical likelihood that areas larger than the area to which a singleMV is applicable move in a similar direction and, therefore, can in somecases be predicted using a similar motion vector derived from MVs ofneighboring area. That results in the MV found for a given area to besimilar or the same as the MV predicted from the surrounding MVs, andthat in turn can be represented, after entropy coding, in a smallernumber of bits than what would be used if coding the MV directly. Insome cases, MV prediction can be an example of lossless compression of asignal (namely: the MVs) derived from the original signal (namely: thesample stream). In other cases, MV prediction itself can be lossy, forexample because of rounding errors when calculating a predictor fromseveral surrounding MVs.

Various MV prediction mechanisms are described in H.265/HEVC (ITU-T Rec.H.265, “High Efficiency Video Coding”, December 2016). Out of the manyMV prediction mechanisms that H.265 offers, described here is atechnique henceforth referred to as “spatial merge”.

Referring to FIG. 1, a current block (101) comprises samples that havebeen found by the encoder during the motion search process to bepredictable from a previous block of the same size that has beenspatially shifted. Instead of coding that MV directly, the MV can bederived from metadata associated with one or more reference pictures,for example from the most recent (in decoding order) reference picture,using the MV associated with either one of five surrounding samples,denoted A0, A1, and B0, B1, B2 (102 through 106, respectively). InH.265, the MV prediction can use predictors from the same referencepicture that the neighboring block is using.

SUMMARY

Aspects of the disclosure provide methods and apparatuses for videoencoding/decoding. In some examples, an apparatus for video decodingincludes processing circuitry. The processing circuitry can beconfigured to receive data of a current block coded with an intra blockcopy (IBC) mode in a bitstream. A block vector of the current block canbe determined based on a history-based block vector prediction (HBVP)table that includes one or more entries each corresponding to apreviously decoded block. Each entry can include a block vector of thecorresponding previously decoded block and a location of thecorresponding previously decoded block. The current block can bereconstructed based on the determined block vector of the current block.In an embodiment, the block vector, a location, a width, and a height ofthe current block is stored in the HBVP table.

Further, each entry can include an x coordinate and y coordinate of acorner of the corresponding previously decoded block. In a furtherembodiment, each entry can include one of corner positions of thecorresponding previously decode block, and a width and a height of thecorresponding previously decoded block.

In an embodiment, the circuitry can be configured to construct a blockvector prediction (BVP) candidate list based on the HBVP table. The BVPcandidate list can include one or more of a first candidate and a secondcandidate. The first candidate can include a first block vector of theblock vectors in the HBVP table. The corresponding previously decodedblock of the first block vector has a location to the left of thecurrent block. The second candidate can include a second block vector ofthe block vectors in the HBVP table. The corresponding previouslydecoded block of the second block vector has a location on top of thecurrent block.

The circuitry is configured to classify the entries in the HBVP tableinto different groups each stored in a classification HBVP table. In anexample, one of the entries of the HBVP table is stored into one of theclassification HBVP tables when a size of the corresponding previouslydecoded block of the one of the entries of the HBVP table satisfies ablock size condition. The block size condition can be that a number ofluma samples of the corresponding previously decoded block of the one ofthe entries of the HBVP table is larger than or equal to a threshold.

In a further example, the entries in the HBVP table are classified intothe classification HBVP tables based on an x coordinate, a y coordinate,or a combination of the x and y coordinates of each of the correspondingpreviously decoded blocks stored in the HBVP table.

In an embodiment, an index indicating one of the classification HBVPtables is received. One entry is selected from the indicatedclassification HBVP tables that correspond to to the most recentlydecoded block among the previously decoded blocks of the one or moreentries in the indicated classification HBVP tables. The block vector ofthe selected one entry is used as a block vector predictor of the blockvector of the current block.

In an embodiment, a BVP candidate list is constructed. The BVP candidatelist includes one or more BVP candidates that each include a blockvector selected from the classification HBVP tables. A BVP candidate canbe selected from the BVP candidate list to be a block vector predictorof the block vector of the current block based on an index received fromthe bitstream. In various embodiments, the current block can be coded inone of a skip mode, a merge mode, or an advanced motion vectorprediction (AMVP) mode.

Aspects of the disclosure also provide a non-transitorycomputer-readable medium storing instructions which when executed by acomputer for video decoding cause the computer to perform the method forvideo decoding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a current block and itssurrounding spatial merge candidates in one example.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system (200) in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system (300) in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 6 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 7 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 8 shows an example of intra picture block compensation.

FIGS. 9A-9D show an example of intra picture block compensation with aone-CTU-size memory for storing reconstructed samples.

FIG. 10 shows an example of spatial merge candidates of a current block(1010).

FIG. 11 shows a flow chart outlining a process (1100) according to someembodiments of the disclosure

FIG. 12 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

1. Video Coding Encoder and Decoder

FIG. 2 illustrates a simplified block diagram of a communication system(200) according to an embodiment of the present disclosure. Thecommunication system (200) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (250). Forexample, the communication system (200) includes a first pair ofterminal devices (210) and (220) interconnected via the network (250).In the FIG. 2 example, the first pair of terminal devices (210) and(220) performs unidirectional transmission of data. For example, theterminal device (210) may code video data (e.g., a stream of videopictures that are captured by the terminal device (210)) fortransmission to the other terminal device (220) via the network (250).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (220) may receive the codedvideo data from the network (250), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (200) includes a secondpair of terminal devices (230) and (240) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (230) and (240)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (230) and (240) via the network (250). Eachterminal device of the terminal devices (230) and (240) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (230) and (240), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 2 example, the terminal devices (210), (220), (230) and(240) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (250) represents any number ofnetworks that convey coded video data among the terminal devices (210),(220), (230) and (240), including for example wireline (wired) and/orwireless communication networks. The communication network (250) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(250) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 3 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (313), that caninclude a video source (301), for example a digital camera, creating forexample a stream of video pictures (302) that are uncompressed. In anexample, the stream of video pictures (302) includes samples that aretaken by the digital camera. The stream of video pictures (302),depicted as a bold line to emphasize a high data volume when compared toencoded video data (304)(or coded video bitstreams), can be processed byan electronic device (320) that includes a video encoder (303) coupledto the video source (301). The video encoder (303) can include hardware,software, or a combination thereof to enable or implement aspects of thedisclosed subject matter as described in more detail below. The encodedvideo data (304) (or encoded video bitstream (304)), depicted as a thinline to emphasize the lower data volume when compared to the stream ofvideo pictures (302), can be stored on a streaming server (305) forfuture use. One or more streaming client subsystems, such as clientsubsystems (306) and (308) in FIG. 3 can access the streaming server(305) to retrieve copies (307) and (309) of the encoded video data(304). A client subsystem (306) can include a video decoder (310), forexample, in an electronic device (330). The video decoder (310) decodesthe incoming copy (307) of the encoded video data and creates anoutgoing stream of video pictures (311) that can be rendered on adisplay (312) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (304),(307), and (309)(e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (320) and (330) can includeother components (not shown). For example, the electronic device (320)can include a video decoder (not shown) and the electronic device (330)can include a video encoder (not shown) as well.

FIG. 4 shows a block diagram of a video decoder (410) according to anembodiment of the present disclosure. The video decoder (410) can beincluded in an electronic device (430). The electronic device (430) caninclude a receiver (431) (e.g., receiving circuitry). The video decoder(410) can be used in the place of the video decoder (310) in the FIG. 3example.

The receiver (431) may receive one or more coded video sequences to bedecoded by the video decoder (410); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (401), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (431) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (431) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (415) may be coupled inbetween the receiver (431) and an entropy decoder/parser (420) (“parser(420)” henceforth). In certain applications, the buffer memory (415) ispart of the video decoder (410). In others, it can be outside of thevideo decoder (410) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (410), forexample to combat network jitter, and in addition another buffer memory(415) inside the video decoder (410), for example to handle playouttiming. When the receiver (431) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (415) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (415) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (410).

The video decoder (410) may include the parser (420) to reconstructsymbols (421) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (410),and potentially information to control a rendering device such as arender device (412)(e.g., a display screen) that is not an integral partof the electronic device (430) but can be coupled to the electronicdevice (430), as was shown in FIG. 4. The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (420) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding. Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (420) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (420) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (420) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (415), so as tocreate symbols (421).

Reconstruction of the symbols (421) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (420). The flow of such subgroup control information between theparser (420) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (410)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (451). Thescaler/inverse transform unit (451) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s)(421) from the parser (420). The scaler/inversetransform unit (451) can output blocks comprising sample values, thatcan be input into aggregator (455).

In some cases, the output samples of the scaler/inverse transform (451)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (452). In some cases, the intra pictureprediction unit (452) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (458). The currentpicture buffer (458) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(455), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (452) has generated to the outputsample information as provided by the scaler/inverse transform unit(451).

In other cases, the output samples of the scaler/inverse transform unit(451) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (453) canaccess reference picture memory (457) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (421) pertaining to the block, these samples can beadded by the aggregator (455) to the output of the scaler/inversetransform unit (451) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (457) from where themotion compensation prediction unit (453) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (453) in the form of symbols (421) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (457) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (455) can be subject to variousloop filtering techniques in the loop filter unit (456). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (456) as symbols (421) from the parser (420), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (456) can be a sample stream that canbe output to the render device (412) as well as stored in the referencepicture memory (457) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (420)), the current picture buffer (458) can becomea part of the reference picture memory (457), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (410) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (431) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (410) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 5 shows a block diagram of a video encoder (503) according to anembodiment of the present disclosure. The video encoder (503) isincluded in an electronic device (520). The electronic device (520)includes a transmitter (540)(e.g., transmitting circuitry). The videoencoder (503) can be used in the place of the video encoder (303) in theFIG. 3 example.

The video encoder (503) may receive video samples from a video source(501) (that is not part of the electronic device (520) in the FIG. 5example) that may capture video image(s) to be coded by the videoencoder (503). In another example, the video source (501) is a part ofthe electronic device (520).

The video source (501) may provide the source video sequence to be codedby the video encoder (503) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (501) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (501) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (503) may code andcompress the pictures of the source video sequence into a coded videosequence (543) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (550). In some embodiments, the controller(550) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (550) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (550) can be configured to have other suitablefunctions that pertain to the video encoder (503) optimized for acertain system design.

In some embodiments, the video encoder (503) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (530) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (533)embedded in the video encoder (503). The decoder (533) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (534). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (534) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (533) can be the same as of a“remote” decoder, such as the video decoder (410), which has alreadybeen described in detail above in conjunction with FIG. 4. Brieflyreferring also to FIG. 4, however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (545) and the parser (420) can be lossless, the entropy decodingparts of the video decoder (410), including the buffer memory (415), andparser (420) may not be fully implemented in the local decoder (533).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (530) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously coded picture fromthe video sequence that were designated as “reference pictures.” In thismanner, the coding engine (532) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (533) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (530). Operations of the coding engine (532) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 5), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (533) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (534). In this manner, the video encoder(503) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (535) may perform prediction searches for the codingengine (532). That is, for a new picture to be coded, the predictor(535) may search the reference picture memory (534) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(535) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (535), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (534).

The controller (550) may manage coding operations of the source coder(530), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (545). The entropy coder (545)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (540) may buffer the coded video sequence(s) as createdby the entropy coder (545) to prepare for transmission via acommunication channel (560), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(540) may merge coded video data from the video coder (503) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (550) may manage operation of the video encoder (503).During coding, the controller (550) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (503) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (503) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (540) may transmit additional datawith the encoded video. The source coder (530) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 6 shows a diagram of a video encoder (603) according to anotherembodiment of the disclosure. The video encoder (603) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (603) is used in theplace of the video encoder (303) in the FIG. 3 example.

In an HEVC example, the video encoder (603) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (603) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (603) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(603) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (603) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 6 example, the video encoder (603) includes the interencoder (630), an intra encoder (622), a residue calculator (623), aswitch (626), a residue encoder (624), a general controller (621), andan entropy encoder (625) coupled together as shown in FIG. 6.

The inter encoder (630) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (622) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (622) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (621) is configured to determine general controldata and control other components of the video encoder (603) based onthe general control data. In an example, the general controller (621)determines the mode of the block, and provides a control signal to theswitch (626) based on the mode. For example, when the mode is the intramode, the general controller (621) controls the switch (626) to selectthe intra mode result for use by the residue calculator (623), andcontrols the entropy encoder (625) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(621) controls the switch (626) to select the inter prediction resultfor use by the residue calculator (623), and controls the entropyencoder (625) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (623) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (622) or the inter encoder (630). Theresidue encoder (624) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (624) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (603) also includes a residuedecoder (628). The residue decoder (628) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (622) and theinter encoder (630). For example, the inter encoder (630) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (622) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (625) is configured to format the bitstream toinclude the encoded block. The entropy encoder (625) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (625) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 7 shows a diagram of a video decoder (710) according to anotherembodiment of the disclosure. The video decoder (710) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (710) is used in the place of the videodecoder (310) in the FIG. 3 example.

In the FIG. 7 example, the video decoder (710) includes an entropydecoder (771), an inter decoder (780), a residue decoder (773), areconstruction module (774), and an intra decoder (772) coupled togetheras shown in FIG. 7.

The entropy decoder (771) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (772) or the inter decoder (780), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (780); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (772). The residual information can be subject to inversequantization and is provided to the residue decoder (773).

The inter decoder (780) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (772) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (773) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (773) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (771) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (774) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (773) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (303), (503), and (603), and thevideo decoders (310), (410), and (710) can be implemented using anysuitable technique. In an embodiment, the video encoders (303), (503),and (603), and the video decoders (310), (410), and (710) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (303), (503), and (503), and the videodecoders (310), (410), and (710) can be implemented using one or moreprocessors that execute software instructions.

II. Intra Block Copy

For hybrid block based video coding, motion compensation from adifferent picture (inter picture motion compensating) is well known.Similarly, motion compensation can also be performed from a previouslyreconstructed area within the same picture. This is referred to as intrapicture block compensation, current picture referencing (CPR), or intrablock copy (IBC). In IBC, a displacement vector that indicates an offsetbetween a current block and a reference block is referred to as a blockvector (BV). Different from a motion vector in motion compensation froma different picture, which can be at any value (positive or negative, ateither x or y direction), a block vector has a few constraints such thatit is ensured that the pointed reference block is available and alreadyreconstructed. Also, for parallel processing consideration, somereference area that is a tile boundary or a wavefront ladder shapeboundary is also excluded for IBC.

The coding of a block vector can be either explicit or implicit. In theexplicit mode (or referred to as advanced motion vector prediction(AMVP) mode in inter coding), the difference between a block vector andits predictor is signaled; in the implicit mode, the block vector isrecovered purely from its predictor, in a similar way as a motion vectorobtained in merge mode. The resolution of a block vector, in someimplementations, is restricted to integer positions; in other systems,it may be allowed to point to fractional positions.

In an embodiment, the use of IBC at block level can be signaled using ablock level flag, referred to as an IBC flag. In an example, the IBCflag is signaled when the current block is not coded in merge mode. Inanother example, the use of IBC can be signaled by a reference indexapproach, and the current decoded picture is treated as a referencepicture. For example, in HEVC Screen Content Coding (SCC), such areference picture is put in the last position of a reference picturelist. This special reference picture is also managed together with othertemporal reference pictures in a decoded picture buffer (DPB).

There are also some variations for IBC, such as treating the IBC as athird mode, which is different from either intra or inter predictionmode. By doing this, the block vector prediction in merge mode and AMVPmode for IBC are separated from regular inter mode. For example, aseparate merge candidate list is defined for IBC mode, where all theentries in the list are all block vectors. Similarly, the block vectorprediction list in IBC AMVP mode consists of block vectors. The generalrules applied to both lists are: the rules may follow the same logic asinter merge candidate list or AMVP predictor list in terms of candidatederivation process. For example, the 5 spatial neighboring locations(shown in FIG. 10) in HEVC or VVC inter merge mode are accessed toderive a merge candidate list for IBC.

FIG. 8 shows an example of intra picture block compensation. A picture(810) under processing (referred to as a current picture) is partitionedinto CTUs (811-825). The CTUs (811-822) have been decoded. The currentCTU (823) is under processing. To decode a IBC-coded current block (801)in the current CTU (823), a block vector (803) can first be determined.Based on the block vector (803), a reference block (802) (also referredto as a prediction block or a predictor block) in the CTU (817) can belocated. Accordingly, the current block (801) can be reconstructed bycombining the reference block (802) with a residual of the current block(801). As shown, the reference block (802) and the current block (801)reside in the same current picture (810).

FIGS. 9A-9D show an example of intra picture block compensation with aone-CTU-size memory for storing reconstructed samples. In a firstexample, a search range of an IBC mode can be constrained to be within acurrent CTU. Thus, an effective memory requirement to store referencesamples for the IBC mode is one CTU size of samples. As an example, a128×128 current CTU can be partitioned into four 64×64 regions.Considering the existing reference sample memory to store reconstructedsamples in a current 64×64 region, 3 more 64×64 sized reference samplememory are required. Based on this fact, in a second example, aneffective search range of the IBC mode can be extended to some part ofthe left CTU while the total memory requirement for storing referencepixels are kept unchanged (1 CTU size, 4 64×64 reference sample memoryin total).

FIGS. 9A-9D show how the one-CTU-size memory is reused for searching aleft CTU. FIGS. 9A-9D each show a left CTU and a right CTU having a sizeof 128×28 samples. Each CTU is partitioned into four 64×64 regions. InFIG. 9A, reconstructed regions (901-903) in the left CTU and a currentregion 904 under processing can be stored in the one-CTU-size memory. InFIG. 9B, two reconstructed regions (911-912) in the left CTU, onereconstructed region (913) in the current CTU, and a current region(914) can be stored in the one-CTU-size memory. In FIG. 9C, areconstructed region (921) in the left CTU, two reconstructed regions(922-923) in the current CTU, and a current region 924 can be stored inthe one-CTU-size memory. In FIG. 9D, three reconstructed regions(931-933) in the current CTU, and a current region 934 can be stored inthe one-CTU-size memory.

In some embodiments, it is required that block vectors signaled in abitstream follow a set of bitstream conformance conditions. As anexample, a valid luma block vector denoted by mvL and in 1/16-pelresolution should obey the following bitstream conformance conditions:

A1: When a derivation process for block availability is invoked with thecurrent luma location (xCurr, yCurr) set equal to (xCb, yCb) and theneighboring luma location (xCb+(mvL[0]>>4), yCb+(mvL[1]>>4)) as inputs,the output shall be equal to TRUE (meaning already constructed thusavailable). The derivation process for block availability is alsoreferred to as a neighboring blocks availability checking process. Thecondition A1 verifies that a top-left corner sample of a reference blockat the location (xCb+(mvL[0]>>4), yCb+(mvL[1]>>4)) is available (alreadyreconstructed).

A2: When the derivation process for block availability is invoked withthe current luma location (xCurr, yCurr) set equal to (xCb, yCb) and theneighboring luma location (xCb+(mvL[0]>>4)+cbWidth−1,yCb+(mvL[1]>>4)+cbHeight−1) as inputs, the output shall be equal toTRUE. The condition A2 verifies that a bottom-right corner sample of areference block at the location (xCb+(mvL[0]>>4)+cbWidth−1,yCb+(mvL[1]>>4)+cbHeight−1) is available.

B1: One or both the following conditions shall be true: The value of(mvL[0]>>4)+cbWidth is less than or equal to 0; and the value of(mvL[1]>>4)+cbHeight is less than or equal to 0. The condition B1verifies that a reference block does not overlap a current block.

C1: The following conditions shall be true:

(yCb+(mvL[1]>>4))>>Ctb Log 2SizeY=yCb>>Ctb Log 2SizeY;

(yCb+(mvL[1]>>4)+cbHeight−1)>>Ctb Log 2SizeY=yCb>>Ctb Log 2SizeY;)

(xCb+(mvL[0]>>4))>>Ctb Log 2SizeY>=(xCb>>Ctb Log 2SizeY)−1; and

(xCb+(mvL[0]>>4)+cbWidth−1)>>Ctb Log 2SizeY<=(xCb>>Ctb Log 2SizeY).

The condition C1 verifies a reference block is located in a current CTUor a left CTU to the current CTU.

C2: When (xCb+(mvL[0]>>>>4))>>Ctb Log 2SizeY is equal to (xCb>>Ctb Log2SizeY)−1, the derivation process for block availability is invoked withthe current luma location (xCurr, yCurr) set equal to (xCb, yCb) and theneighboring luma location (((xCb+(mvL[0]>>4)+CtbSizeY)>>(Ctb Log2SizeY−1))<<(Ctb Log 2SizeY−1), ((yCb+(mvL[1]>>4))>>(Ctb Log2SizeY−1))<<(Ctb Log 2SizeY−1)) as inputs, the output shall be equal toFALSE (not constructed yet). The condition C2 verifies a referenceregion (e.g., the region (921) in FIG. 9C) in a left CTU corresponds toa region in a current CTU that is not constructed yet.

III. Spatial Merge Candidates of a Current Block

FIG. 10 shows five spatial merge candidates of a current block (1010).The spatial merge candidates can be used for constructing a predictorlist for block vector prediction of the current block (1010). Forexample, the current block (1010) is under construction with a skipmode, a merge mode, or a AMVP mode. A candidate list can be constructed.Candidates on the candidate list can be selected from spatial candidatepositions A1, A0, B2, B0, and B1. In one example, availability of thespatial candidate positions are checked in the following order, A0, B0,B1, A1, and B2. When available, motion information at the candidateposition can be added to the candidate list as a candidate. An index tothe candidate list can be received in a bitstream. A candidatecorresponding to the index can be used as a motion vector prediction (orpredictor) to determine a motion vector of the current block 1010.

IV. History Based Motion Vector Prediction (HMVP)

In some example, a history based motion vector prediction (HMVP) schemeis used for coding a block. For example, HMVP merge candidates are addedto a merge list after spatial motion vector prediction (SMVP) andtemporal motion vector prediction (TMVP) candidates. In this method,motion information of a previously coded block is stored in a table(referred to as a HMVP table) and used as a motion vector predictor(MVP) for a current CU. The HMVP table with multiple HMVP candidates ismaintained during an encoding or decoding process. The HMVP table isreset (emptied) when a new CTU row is encountered in some examples.Whenever there is a non-subblock inter-coded CU, the associated motioninformation is added to the last entry of the HMVP table as a new HMVPcandidate in some examples.

In an embodiment, a HMVP table size S is set to be 6, which indicates upto 6 HMVP candidates may be added to the HMVP table. When inserting anew motion candidate to the HMVP table, a constrained first-in-first-out(FIFO) rule is utilized. A redundancy check is firstly applied to findwhether there is an identical HMVP in the HMVP table. If found, theidentical HMVP is removed from the table and all the HMVP candidatesafterwards are moved forward.

HMVP candidates can be used in a merge candidate list constructionprocess. In an example, the latest several HMVP candidates in the HMVPtable are checked in order and inserted to the candidate list after TMVPcandidates. Redundancy check is applied on the HMVP candidates againstspatial or temporal merge candidates.

In an embodiment, to reduce the number of redundancy check operations,the following simplifications are introduced: (1) Number of HMVPcandidates used for merge list generation is set as (N<=4) ? M: (8−N),wherein N indicates number of existing candidates in the merge list andM indicates number of available HMVP candidates in the HMVP table. (2)Once the total number of available merge candidates reaches themaximally allowed merge candidates minus 1, the merge candidate listconstruction process from HMVP is terminated in an example.

V. HBVP Table Based Intra Block Copy (IBC)

In various embodiments, an IBC mode operates as a separate mode frominter mode (motion compensation from a picture different from a currentpicture). A separate history buffer, referred to as history-based blockvector prediction (HBVP) buffer, is used for storing previouslyprocessed (encoded at an encoder side/decoded at a decoder side) IBCblock vectors. When processing a current block coded with the IBC mode,either at an encoder side or a decoder side, a block vector of thecurrent block can be determined based on the HBVP buffer. The HBVPbuffer can also be referred to as an HBVP table or an HBVP list. In thisdetailed descriptions, HBVP buffer, HBVP table, and HBVP list are usedinterchangeably.

Embodiments described herein may be used separately or combined in anyorder. Further, each of methods (or embodiments), encoder, and decodermay be implemented by processing circuitry (e.g., one or more processorsor one or more integrated circuits). In one example, the one or moreprocessors execute a program that is stored in a non-transitorycomputer-readable medium. In the detailed descriptions, the term blockmay be interpreted as a prediction block, a coding block, or a codingunit (CU).

Embodiment A

When adding a block vector of an already processed block into an HBVPtable, position (or location) information of the already processed blockcan be recorded in the HBVP table. In other words, for each entry in theHBVP table, in addition to block vector information, a location of acoded block (previously encoded or decoded block) which the block vectoris associated with is also stored.

In an example, a redundancy check is not performed when adding a newblock vector and associated location information to an HBVP tablebecause each position of coded blocks is different. In another example,a redundancy check is performed when adding a new block vector andassociated location information to an HBVP table. For example, the newblock vector is compared with block vectors previously stored in theHBVP table. If a similar or identical old block vector is found, the oldentry including the old block vector can be removed, and an entryincluding the new block vector and associated location information canbe added to the HBVP table as a most recent candidate.

The location of a coded block can be represented by one of the fourcorners of the coded block in various examples. For example, x and ycoordinates of a corner of the code block can be used to indicate thelocation. In an example, the location of a coded block is represented bya position of the bottom-right corner of the coded block. In anotherexample, the location of a coded block can be represented by a positionof the bottom-left corner of the coded block.

In an example, the location of a coded block can be represented by aposition of one of the four corners of the coded block plus size (e.g.,a width and a height) information of the coded block.

In an example, an HBVP table is reset (e.g., emptied) at the beginningof each CTU row. Under such a configuration, position information ofentries in the HBVP table can each be recorded using a relative y offsetfrom the respective CTU upper edge for the y coordinate of eachrespective coded block. In another embodiment, an HBVP table is reset atthe beginning of each CTU. Accordingly, position information of entriesin the HBVP can each be recorded using the relative x and y offsets fromthe respective CTU origin for the x and y coordinates of each respectivecoded block. In a further example, when recording x and y coordinates ofan entry in the HBVP table, offsets from the respective CTU origin ofthe respective coded block are recorded irrelevant with the HBVP tablereset operations.

Embodiment B

In some examples, a block vector prediction (BVP) candidate list isconstructed based on an HBVP table. When selecting entries from the HBVPto be BVP candidates on the BVP candidate list, locations (or positions)of entries (referring to positions of coded blocks corresponding torespective entries) are considered.

In an example, a position of a current block and a position of an entryare compared. Position information of the entry is adjusted if theentry's position is in the bottom-right position of the current block.Based on the adjusted position information, the location relationshipbetween the coded block and the current block can be determined.

For example, when calculating the relative position of the current blockto one entry in the HBVP table, if both of the current block's x and ycoordinates is smaller than the entry's x and y coordinates,respectively (meaning the previously coded block is in the bottom-rightposition relative to the current block, which is impossible), an offsetof (−CTU width, 0) is added to the entry's coordinates when performingthe calculation. As a result, such an entry is moved to the left of thecurrent block (meaning the respective block vector now is from the CTUto the left of current CTU).

In an example, an entry located to the left of a current block can beselected from an HBVP table and used as a block vector predictor (e.g.,added to a BVP candidate list). For example, an entry in the HBVP tableincluding an x coordinate corresponding to a top-left corner of a codedblock. If the x coordinate is smaller than that of a top-left corner ofthe current block, it can be determined the entry (or the correspondingcoded block) is located to the left of the current block.

Similarly, a block vector can be selected from an HBVP table that is ontop of a current block. For example, an entry in the HBVP tableincluding a y coordinate corresponding to a top-left corner of a codedblock. If the y coordinate is smaller than that of a top-left corner ofthe current block, it can be determined the entry (or the correspondingcoded block) is located on top of the current block.

Accordingly, in some examples, a BVP candidate list can be constructedbased on entries selected from an HBVP table that are to the left or ontop of a current block.

In some examples, a maximum number of 2*N predictors are adopted topredict a block vector of a current block (e.g., that are added to a BVPcandidate list). In one example, N=1, then one of the 2*N predictors isfrom left positioned entries (referring to entries located to the leftof the current block) in a HBVP table and the other one of the 2*Npredictors is from top positioned entries (referring to entries locatedon top of the current block) in the HBVP able. In another example N=2,then the order of the predictors in the BVP candidate list may be, 1stleft->1st top->2nd left->2nd top, assuming there are enough entries inthe HBVP table. When there are no enough entries, the corresponding itemin the predictor list (the BVP candidate list) can be empty and befilled up with a next item.

In some examples, started from the most recently coded entry in a HBVPtable, a first entry that is to the left of a current block is selectedas a left predictor. A next entry that is to the left of the currentblock is selected as a second left predictor. In this way, leftpredictors can be successively selected.

In some examples, started from the most recently coded entry in a HBVPtable, a first entry that is on top of a current block can be selectedas a first top predictor. A next entry that is on top of the currentblock can be selected as a second top predictor. In this way, toppredictors can be successively selected.

In an example, a two-candidate predictor list (BVP candidate list) isconstructed by scanning the first N HBVP entries in a HBVP table. Thefirst N entries can be the most recently coded N entries or can be themost previously coded N entries in different examples. For example, Ncan be smaller than a size S of the HBVP table. The first entry to theleft of a current block can be put as the first candidate in thepredictor list. The first entry on top of the current block can be putas the 2nd candidate in the predictor list. If there are only top oronly left candidates in the HBVP table, then the first two availableentries cab be selected as the predictors.

Embodiment C

In some embodiments, a BVP candidate list (a predictor list) can beconstructed in the following way. A block vector in a HBVP table isderived as a predictor if the block vector has an associated locationnext to the current block. For example, entries in the HBVP table can bescanned according to an order, for example, from the latest to theoldest. If an entry is next to the current block (the entry includes alocation next to the current block), the block vector of this entry isput in the predictor list. This process can continue until a maximumnumber of candidates in the predictor list has reached. For example, inFIG. 10, the 5 spatial neighboring positions are considered to be nextto the current block (1010). Entries in the HBVP table having locationscorresponding to the five positions in FIG. 10 can be considered, andselected as candidates in the predictor list according to a certainorder (e.g., A0, B0, B1, A1, and B2).

In an example, if a block vector in the HBVP buffer is not next to thecurrent block, it may be put in the later positions in the predictorlist after the spatial neighboring entries. In another example, if ablock vector in the HBVP buffer is not next to current block, it may notbe used in the predictor list.

Embodiment D

In some examples, when putting a block vector into a predictor list, aredundancy check can be performed to make sure the new predictor isdifferent from other existing predictors in the predictor list.

Embodiment E

In various examples, a predictor list can be constructed based on anHBVP table, and used in a merge mode, a skip mode, or an AMVP mode(vector prediction with difference coding) for coding a block vector(block vector prediction) of a current block.

Embodiment F

In an embodiment, multiple HBVP tables can be maintained during adecoding process. Each HBVP table can be associated with a differentcriterion for taking a new coded block vector (a block vector of apreviously decoded block). In this way, block vectors of coded blockscan be categorized into different groups and stored into thecorresponding HBVP tables. When coding a current IBC-coded block, one ormore block vectors can be selected from those separate HBVP tables andused as predictors for coding a block vector of the current block.Similarly, entries in those HBVP tables can each include a block vectorof a coded block, a location (x and y coordinates) of the code block, asize (a width and a height) of the coded block, or other relatedinformation.

In a first example, the criterion for one of the HBVP tables taking anew block vector of a coded block is that the coded block satisfies ablock size condition. A block size of the coded block can be measured invarious ways. For example, the block size can be a number of lumasamples in the coded block calculated by multiply a width with a heightof the coded block. In an example, the block size condition is that theblock size is larger than or equal to a threshold T_size1 and smallerthan another threshold T_size2. In an example, the block size conditionis that the block size is larger than or equal to a threshold.

In a second example, the criterion for one of the HBVP tables taking anew block vector of a coded block is that the coded block has a top-leftcorner's x coordinate xc satisfying the following condition: xc %ctuSizeY is greater than or equal to a threshold T_x0 and is smallerthan another threshold T_x1. The symbol % denotes a modulo operation,and ctuSizeY represents a size of CTU.

In a third embodiment, the criterion for one of the HBVP tables taking anew block vector of a coded block is that the coded block has a top-leftcorner's y coordinate yc satisfying the following condition: yc %ctuSizeY is greater than or equal to a threshold T_y0 and is smallerthan another threshold T_y1.

In a fourth example, the criterion for one of the HBVP tables taking anew block vector of a code block is that the coded block has abottom-right corner's x coordinate xc satisfying the followingcondition: xc % ctuSizeY is greater than or equal to a threshold T_x0and is smaller than another threshold T_x1.

In a fifth example, the criterion for one of the HBVP tables taking anew block vector of a coded block is that the coded block has abottom-right corner's y coordinate yc satisfying the followingcondition: yc % ctuSizeY is greater than or equal to a threshold T_y0and is smaller than another threshold T_y1.

In the above examples, a pruning process may be applied when putting anew block vector into an HBVP table. For example, when an entry in theHBVP table with the same block vector value as that of the new blockvector is found, the entry may be removed. A new entry including the newblock vector can be put in a position for storing an entry including ablock vector of the most recently coded block.

Embodiment G

In an embodiment, one or more HBVP tables are maintained for blockvector prediction of IBC-coded blocks. Each HBVP table is associatedwith a specific criterion for taking a new block vector. Assuming N HBVPtables in total are created and maintained. N is a positive integernumber and is greater than or equal to 1.

In a first example, for each HBVP table that does not have any entriesstored, a set of default block vector predictors are used to fill up theHBVP table. For example, a default block vector predictor can be a zerovalued block vector (x and y coordinates being zero).

In a second example, an index pointing to one of the N HBVP tables canbe received from a bitstream at a decoder. In response, an entry in theHBVP table indicated by the index can be selected for block vectorprediction of a current block. For example, a most recent entry (a mostrecently added one) in the HBVP table indicated by the index can beselected as a block vector predictor of a current IBC-coded block. Foranother example, a least recent entry (a least recently coded one) inthe HBVP table indicated by the index is selected as a block vectorpredictor of a current IBC-code block.

Embodiment H

In an embodiment, a single HBVP table, HBVP0, is maintained during adecoding process at a decoder. While decoding a current IBC-coded block,in order to determine a block vector predictor of the current block,entries in the HBVP0 are categorized into different groups. Each groupis stored into a separate HBVP table that is referred to as aclassification HBVP table. Each classification HBVP table can beassigned with a specific criterion for taking an entry from the HBVP0.The categorization operations can thus be based on those criteria.

For example, the HBVP0 can have a size of M. A number of theclassification HBVP tables can be N that is smaller than or equal to M.The classification HBVP tables can be represented to be from HBVP1 toHBVPN.

For example, the criteria for categorizing newly coded block vectors asdescribed in Embodiment F can be used for categorizing the entries ofthe HBVP0 into the tables from HBVP1 to HBVPN. Criteria different fromthat in Embodiment F can be employed in other examples. A pruningprocess may be applied when putting a new entry into the HBVPx table(x=0, 1, . . . , N). For example, when there is an old entry in theHBVPx with the same block vector value as that of the new entry, the oldentry may be removed and the new one is put in a position for storinginformation of the most recently coded block.

In an example, after the tables of HBVP1 to HBVPN are generated, anentry can be selected from one of the tables of HBVP1 to HBVPN accordingto an index received from a bitstream. A block vector in the selectedentry can be used as a block vector predictor of the current block.

In a first case, the index can indicate one of the tables of HBVP1 toHBVPN. In response to receiving the index, a latest entry (most recententry) can be selected from the HBVP table indicated by the index.

In a second case, a predictor list can first be constructed by selectingentries from the tables of HBVP1 to HBVPN according to some rules (e.g.,as described in Embodiment C). The index can indicate a candidate on thepredictor list. In response to receiving the index, the candidate on thepredictor list can be used as a block vector predictor of the currentblock.

VI. Examples of HBVP Table Based IBC Mode Decoding Process

FIG. 11 shows a flow chart outlining a process (1100) according to someembodiments of the disclosure. The process (1100) can be used in thereconstruction of an IBC-coded block, so to generate a prediction blockfor the block under reconstruction. In various embodiments, the process(1100) are executed by processing circuitry, such as the processingcircuitry in the terminal devices (210), (220), (230) and (240), theprocessing circuitry that performs functions of the video decoder (310),the processing circuitry that performs functions of the video decoder(410), and the like. In some embodiments, the process (1100) isimplemented in software instructions, thus when the processing circuitryexecutes the software instructions, the processing circuitry performsthe process (1100). The process starts at (S1101) and proceeds to(S1110).

At (S1110), a HBVP table can be maintained during a process of decodinga picture at a decoder. For example, the HBVP table can include one ormore entries each corresponding to a previously decoded IBC-coded block.Each entry can include a block vector of the corresponding previouslydecoded block and a location of the corresponding previously decodedblock. The location can be an x coordinate and a y coordinate of one offour corners of the previously coded block. In an example, each entrycan further include size information (e.g., a width and a height) of therespective previously decoded block.

At (S1120), data of a current block coded with an IBC mode can bereceived in a bitstream. For example, the data can include a set ofblock-level syntax elements corresponding to the current block. One ofthe syntax elements can indicate the current block is coded with the IBCmode.

At (S1130), a block vector of the current block can be determined basedon the HBVP table. In order to determine the block vector of the currentblock, a block vector predictor of the block vector of the current blockcan first be determined.

In an example, a BVP candidate list can be constructed based on the HBVPtable. A candidate is then selected from the BVP candidate list, forexample, based on an index to the candidate on the BVP candidate listreceived in the bitstream. The selected candidate can include a blockvector used as the block vector predictor. The BVP candidate list caninclude one or more of a first candidate and a second candidate. Thefirst candidate can include a first block vector of the block vectors inthe HBVP table. The corresponding previously decoded block of the firstblock vector has a location to the left of the current block. The secondcandidate can include a second block vector of the block vectors in theHBVP table. The corresponding previously decoded block of the secondblock vector can have a location on top of the current block.

In some examples, in order to determine the block vector predictor, theentries in the HBVP table are first classified into different groupseach stored in a classification HBVP table. Each classification HBVPtable can be associated with a criterion for taking a new entry. Forexample, one of the entries of the HBVP table is stored into one of theclassification HBVP tables when a size of the corresponding previouslydecoded block of the one of the entries of the HBVP table satisfies ablock size condition. For example, the block size condition can be thata number of luma samples of the corresponding previously decoded blockof the one of the entries of the HBVP table is larger than or equal to athreshold.

For another example, the entries in the HBVP table can be classifiedinto the classification HBVP tables based on an x coordinate, a ycoordinate, or a combination of the x and y coordinates of each of thecorresponding previously decoded blocks stored in the HBVP table.Accordingly, the entries of the coded blocks located at differentpositions with respect to the current block can be stored into differentclassification tables.

Based on the classification HBVP tables, the block vector predictor canbe determined. In an example, an index indicating one of theclassification HBVP tables can be received in the bit stream.Accordingly, one entry can be selected from the indicated classificationHBVP tables. The selected entry can correspond to the most recentlydecoded block among the decoded blocks of the entries in the indicatedclassification HBVP tables. The block vector of the selected entry canbe used as the block vector predictor of the block vector of the currentblock.

In another example, a BVP candidate list can be constructed based on theclassification HBVP tables. The BVP candidate list can include one ormore BVP candidates that each include a block vector selected from theclassification HBVP tables. Subsequently, a BVP candidate can beselected from the BVP candidate list to be the block vector predictor ofthe block vector of the current block based on an index received fromthe bitstream.

After the block vector predictor is determined, the block vector of thecurrent block can be determined accordingly. For example, the currentblock can be coded with the IBC mode in one of a skip mode, a mergemode, or an AMVP mode. For the skip mode and the merge mode, the blockvector predictor can be used as the block vector of the current block.For the AMVP mode, a vector difference can be received in the bitstream,and added to the block vector predictor to form the block vector of thecurrent block.

At (S1140), the current block can be reconstructed based on thedetermined block vector of the current block. For example, a referenceblock can be determined in the already decoded region of the picturebased on the block vector, and combined with a residual of the currentblock to form a reconstructed block.

At (S1150), the HBVP table can be updated with the block vector of thecurrent block. For example, the block vector of the current block, alocation, a width, and a height of the current block can be stored inthe HBVP table. A redundancy check may be performed when updating theHBVP table. The process (1100) can then proceed to (S1199), andterminate at (S1199).

VII. Computer System

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 12 shows a computersystem (1200) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 12 for computer system (1200) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1200).

Computer system (1200) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1201), mouse (1202), trackpad (1203), touchscreen (1210), data-glove (not shown), joystick (1205), microphone(1206), scanner (1207), camera (1208).

Computer system (1200) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1210), data-glove (not shown), or joystick (1205), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1209), headphones(not depicted)), visual output devices (such as screens (1210) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability-some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1200) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1220) with CD/DVD or the like media (1221), thumb-drive (1222),removable hard drive or solid state drive (1223), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1200) can also include an interface (1254) to one ormore communication networks (1255). Networks can for example bewireless, wireline, optical. Networks can further be local, wide-area,metropolitan, vehicular and industrial, real-time, delay-tolerant, andso on. Examples of networks include local area networks such asEthernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G,LTE and the like, TV wireline or wireless wide area digital networks toinclude cable TV, satellite TV, and terrestrial broadcast TV, vehicularand industrial to include CANBus, and so forth. Certain networkscommonly require external network interface adapters that attached tocertain general purpose data ports or peripheral buses (1249) (such as,for example USB ports of the computer system (1200)); others arecommonly integrated into the core of the computer system (1200) byattachment to a system bus as described below (for example Ethernetinterface into a PC computer system or cellular network interface into asmartphone computer system). Using any of these networks, computersystem (1200) can communicate with other entities. Such communicationcan be uni-directional, receive only (for example, broadcast TV),uni-directional send-only (for example CANbus to certain CANbusdevices), or bi-directional, for example to other computer systems usinglocal or wide area digital networks. Certain protocols and protocolstacks can be used on each of those networks and network interfaces asdescribed above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1240) of thecomputer system (1200).

The core (1240) can include one or more Central Processing Units(CPU)(1241), Graphics Processing Units (GPU) (1242), specializedprogrammable processing units in the form of Field Programmable GateAreas (FPGA)(1243), hardware accelerators for certain tasks (1244),graphics adapter (1250), and so forth. These devices, along withRead-only memory (ROM) (1245), Random-access memory (1246), internalmass storage such as internal non-user accessible hard drives, SSDs, andthe like (1247), may be connected through a system bus (1248). In somecomputer systems, the system bus (1248) can be accessible in the form ofone or more physical plugs to enable extensions by additional CPUs. GPU,and the like. The peripheral devices can be attached either directly tothe core's system bus (1248), or through a peripheral bus (1249). InFIG. 12, the screen (1210) is connected to the graphics adapter (1250).Architectures for a peripheral bus include PCI, USB, and the like.

CPUs (1241), GPUs (1242), FPGAs (1243), and accelerators (1244) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1245) or RAM (1246). Transitional data can be also be stored in RAM(1246), whereas permanent data can be stored for example, in theinternal mass storage (1247). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1241), GPU (1242), massstorage (1247), ROM (1245), RAM (1246), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1200), and specifically the core (1240) can providefunctionality as a result of processor(s)(including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1240) that are of non-transitorynature, such as core-internal mass storage (1247) or ROM (1245). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1240). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1240) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1246) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1244)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (1C)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

Appendix A: Acronyms AMVP: Advanced Motion Vector Prediction ASIC:Application-Specific Integrated Circuit

BMS: benchmark set

BV: Block Vector CAN Bus: Controller Area Network Bus CD: Compact DiscCPR: Current Picture Referencing CPUs: Central Processing Units CRT:Cathode Ray Tube CTBs: Coding Tree Blocks CTU: Coding Tree Unit CU:Coding Unit DPB: Decoded Picture Buffer DVD: Digital Video Disc FIFO:First-in-First-out FPGA: Field Programmable Gate Areas GOPs: Groups ofPictures GPUs: Graphics Processing Units

GSM: Global System for Mobile communications

HBVP: History-based Block Vector Prediction

HEVC SCC: HEVC screen content coding

HEVC: High Efficiency Video Coding HMVP: History-based Motion VectorPrediction HRD: Hypothetical Reference Decoder IBC: Intra Block Copy IC:Integrated Circuit

JEM: joint exploration model

LAN: Local Area Network LCD: Liquid-Crystal Display LTE: Long-TermEvolution MV: Motion Vector

MVP: Motion vector predictor

OLED: Organic Light-Emitting Diode PBs: Prediction Blocks PCI:Peripheral Component Interconnect PLD: Programmable Logic Device PUs:Prediction Units RAM: Random Access Memory ROM: Read-Only Memory SEI:Supplementary Enhancement Information SNR: Signal Noise Ratio

SSD: solid-state drive

TMVP: Temporal Motion Vector Prediction TUs: Transform Units, USB:Universal Serial Bus

VTM: VVC test model

VUI: Video Usability Information

VVC: versatile video coding

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method of video decoding at a video decoder,comprising: receiving data of a current block coded with an intra blockcopy (IBC) mode in a bitstream; determining a block vector of thecurrent block based on a history-based block vector prediction (HBVP)table that includes one or more entries each corresponding to apreviously decoded block, each entry including a block vector of thecorresponding previously decoded block and a location of thecorresponding previously decoded block; and reconstructing the currentblock based on the determined block vector of the current block.
 2. Themethod of claim 1, further comprising: storing the block vector, alocation, a width, and a height of the current block in the HBVP table.3. The method of claim 1, wherein each entry includes an x coordinateand y coordinate of a corner of the corresponding previously decodedblock.
 4. The method of claim 1, wherein each entry includes one ofcorner positions of the corresponding previously decode block, and awidth and a height of the corresponding previously decoded block.
 5. Themethod of claim 1, wherein the determining the block vector of thecurrent block based on the HBVP table further includes: constructing ablock vector prediction (BVP) candidate list based on the HBVP table,the BVP candidate list including one or more of: a first candidate thatincludes a first block vector of the block vectors in the HBVP table,the corresponding previously decoded block of the first block vectorhaving a location to the left of the current block, or a secondcandidate that includes a second block vector of the block vectors inthe HBVP table, the corresponding previously decoded block of the secondblock vector having a location on top of the current block.
 6. Themethod of claim 1, wherein the current block is coded in one of a skipmode, a merge mode, or an advanced motion vector prediction (AMVP) mode.7. The method of claim 1, wherein the determining the block vector ofthe current block based on the HBVP table further includes: scanning theentries in the HBVP table according to an order, and adding the blockvector of one of the entries in the HBVP table to a BVP candidate listwhenever the respective entry having a location next to the currentblock until a maximum number of the BVP candidate list is reached.
 8. Anapparatus of video decoding, comprising circuitry configured to: receivedata of a current block coded with an intra block copy (IBC) mode in abitstream; determine a block vector of the current block based on ahistory-based block vector prediction (HBVP) table that includes one ormore entries each corresponding to a previously decoded block, eachentry including a block vector of the corresponding previously decodedblock and a location of the corresponding previously decoded block; andreconstruct the current block based on the determined block vector ofthe current block.
 9. The apparatus of claim 13, wherein the circuitryis further configured to: store the block vector, a location, a width,and a height of the current block in the HBVP table.
 10. The apparatusof claim 13, wherein each entry includes an x coordinate and ycoordinate of a corner of the corresponding previously decoded block.11. The apparatus of claim 13, wherein each entry includes one of cornerpositions of the corresponding previously decode block, and a width anda height of the corresponding previously decoded block.
 12. Theapparatus of claim 13, wherein the circuitry is further configured to:construct a block vector prediction (BVP) candidate list based on theHBVP table, the BVP candidate list including one or more of: a firstcandidate that includes a first block vector of the block vectors in theHBVP table, the corresponding previously decoded block of the firstblock vector having a location to the left of the current block, or asecond candidate that includes a second block vector of the blockvectors in the HBVP table, the corresponding previously decoded block ofthe second block vector having a location on top of the current block.13. The apparatus of claim 8, wherein the current block is coded in oneof a skip mode, a merge mode, or an advanced motion vector prediction(AMVP) mode.
 14. The apparatus of claim 8, wherein the circuitry isfurther configured to: scan the entries in the HBVP table according toan order, and add the block vector of one of the entries in the HBVPtable to a BVP candidate list whenever the respective entry having alocation next to the current block until a maximum number of the BVPcandidate list is reached.
 15. A non-transitory computer-readable mediumstoring instructions that, when executed by a processor, cause theprocessor to perform a method of video decoding, the method comprising:receiving data of a current block coded with an intra block copy (IBC)mode in a bitstream; determining a block vector of the current blockbased on a history-based block vector prediction (HBVP) table thatincludes one or more entries each corresponding to a previously decodedblock, each entry including a block vector of the correspondingpreviously decoded block and a location of the corresponding previouslydecoded block; and reconstructing the current block based on thedetermined block vector of the current block.
 16. The non-transitorycomputer-readable medium of claim 13, wherein the method furthercomprises: storing the block vector, a location, a width, and a heightof the current block in the HBVP table.
 17. The non-transitorycomputer-readable medium of claim 13, wherein each entry includes an xcoordinate and y coordinate of a corner of the corresponding previouslydecoded block.
 18. The non-transitory computer-readable medium of claim13, wherein each entry includes one of corner positions of thecorresponding previously decode block, and a width and a height of thecorresponding previously decoded block.
 19. The non-transitorycomputer-readable medium of claim 13, wherein the determining the blockvector of the current block based on the HBVP table further includes:constructing a block vector prediction (BVP) candidate list based on theHBVP table, the BVP candidate list including one or more of: a firstcandidate that includes a first block vector of the block vectors in theHBVP table, the corresponding previously decoded block of the firstblock vector having a location to the left of the current block, or asecond candidate that includes a second block vector of the blockvectors in the HBVP table, the corresponding previously decoded block ofthe second block vector having a location on top of the current block.20. The non-transitory computer-readable medium of claim 13, wherein thecurrent block is coded in one of a skip mode, a merge mode, or anadvanced motion vector prediction (AMVP) mode.